1. Field of the Invention
The present invention relates to an imaging apparatus with an interchangeable lens unit and a method for controlling the same, and, in particular, to a communication system optimum for each type of a lens unit to be attached and each function of the lens unit, and to a technique whereby to correct image degradation resulting from optical characteristics of the lens unit.
The present invention also relates to a communication processing between a camera and a lens unit suited for correction of image degradation resulting from optical characteristics of the lens unit, and to the lens unit.
2. Description of the Related Art
An imaging apparatus such as a digital camera and a digital video camera is always required to have a high-quality output image. This also holds true of the digital camera and the digital video camera which are provided with an interchangeable lens unit.
Along with that, a control technique for the lens unit has been more and more complicated. For example, an initial positioning for a focus mechanism and a diaphragm mechanism, which form the lens unit, is made to perform high-accuracy control. Also as an example, there is a mechanism for correcting an optical characteristic, which is one of factors degrading image quality, of the lens unit used for capturing an object image. A light falloff at edges, distortion aberration, and chromatic aberration of magnification are cited as examples of the optical characteristic causing image degradation. It is difficult to realize a lens unit completely eliminating the above factors. For this reason, a technique is known in which a captured image is subjected to image processing to correct image degradation caused by the optical characteristic (an optical correction technique).
Even the same lens unit changes in its optical characteristic depending on values of optical parameters, such as a focal length (angle of view of a zoom lens), a photographing distance (a focusing distance) and an aperture value. Therefore, if the image degradation caused by the optical characteristic is corrected by the image processing, an optical correction value corresponding to the optical parameter in capturing an image needs to be used to accurately correct the image degradation.
Japanese Patent Application Laid-Open No. 2005-286482 discusses a method for determining an optical correction quantity based on a polynomial approximate equation obtained from transition of a distortion correction quantity according to a zoom position of the zoom lens (focal length).
A conventional technique discussed in Japanese Patent Application Laid-Open No. 2005-286482 does not consider what type of communication system is used for switching to perform an appropriate communication between a camera and a lens.